pub fn odd_fibnacci_sum(threshold: u32) -> u32 {
    let mut fbi_1 = 0u32;
    let mut fbi_2 = 1u32;
    let mut sum = 0;

    while fbi_2 < threshold {
        if fbi_2 % 2 != 0 {
            sum += fbi_2;
        }
        let next = fbi_1 + fbi_2;
        fbi_1 = fbi_2;
        fbi_2 = next;
    }
    sum
}
